Abstract

Background: Human and dog invasive bladder cancers share similar attributes, such as pathologic changes, response to chemotherapy, and extremely poor prognosis. Via combinatorial chemistry approach, we previously identified a novel bladder cancer-specific ligand, PLZ4, that can specifically bind to both human and dog bladder cancer cells in vitro and in vivo. We also developed a micelle nanocarrier drug delivery system with multifunctional loading capacity. Here, we assessed whether the targeting micelles impregnated with PLZ4 on the surface could promote targeting efficacy against both human and dog bladder cancers for diagnostic imaging and therapeutic purposes. Materials and Methods: Micelle-building monomers (i.e., telodendrimers) were synthesized through conjugation of polyethylene glycol with cholic acid cluster at one end and PLZ4 at the other end, which then self-assembled in aqueous solution to form micelles. Near-infrared dye DiD and chemotherapeutic drugs (paclitaxel or daunorubicin) were co-loaded for the experiments. Cellular uptake and distribution of nanomicelles were evaluated by fluorescence intensity and high resolution topography, while drug delivery efficacy was monitored by cytotoxicity assay. Using orthotopic/xenograft mouse model generated from human clinical bladder cancer specimen or dog bladder cancer line, in vivo and ex vivo fluorescence imaging as well as efficacy study were performed. Results: Compared to non-targeting micelles, targeting PLZ4-decorated-micelles loaded with an imaging agent DiD and chemotherapeutic drugs were more efficient in dye delivery, and caused a comparable to higher degree of cytotoxicity with free drugs in bladder cancer cell lines. According to topography, targeting micelles tended to localize at the membrane, perinuclear, and nucleus. In vivo and ex vivo orthotopic xenograft studies showed that both targeting (14.3X of free dye, p<0.01) and non-targeting micelles (9.6X, p<0.01) rapidly accumulated at the tumor sites, while targeting micelles exhibited significantly higher efficiency in homing property than non-targeting micelles (p<0.05). Considerably higher DiD signal was microscopically observed in targeting group than non-targeting group as well as free dye group, but all exhibited similar blood vessel density. Our preliminary efficacy study also supported a better drug delivery efficiency using targeting micelle formulation than non-targeting micelles/free drug in mouse xenografts formed from human clinical bladder tumors. Conclusions: Targeting micelles impregnated with PLZ4 can selectively and efficiently target both human and dog bladder cancer cells and can be potentially developed as imaging and therapeutic agents in both human and veterinary medicine. Preclinical studies of targeting micelles can be performed in dogs with spontaneous bladder cancer before proceeding to human patients.